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PubMed1980

Predictive value and efficiency of hematology data.

Laboratory test results and procedures can be evaluated at four levels:1. Analytic analysis of laboratory test: precision, technical sensitivity, technical specificity; 2. Diagnostic analysis of laboratory test: diagnostic sensitivity, diagnostic specificity, Youden index, likelihood ratio, etc.; 3. Operational analysis of laboratory test: predictive value of positive result, predictive value of negative result, efficiency, discriminant function, etc.; 4. Medical decision-making analysis of laboratory test: threshold probability, cost-benefit analysis, solving the decision tree. Analysis of results or selection of tests can occur at any level, without knowledge of the test's evaluation or performance at the remaining levels. Alternatively, the development of new laboratory tests can proceed from level 1 to level 4, or vice versa. Unfortunately, the former is usually the case and most of the tests in use today have never been evaluated at the medical decision-making level (level 4). Recent efforts at developing automated WBC differential counters represent a disproportionate amount of time and energy expended at level 1, and typify our backward approach to laboratory medicine. In thinking about the development of new diagnostic tests, we should begin at level 4 to characterize the properties and specifications that the test must meet. As an example, an in vitro test for the diagnosis of pulmonary embolism could be characterized in this fashion with criteria specified at each of the lower levels. Returning to the question of "How good should a laboratory test be?", we can see that the answer must come from an analysis of the benefit-cost equation (level 4). Figure 2 is a plot of the net benefit and cost of treatment versus the threshold probability. Since the threshold probability defines how certain one must be of the diagnosis before proceeding with treatment, it serves as a minimum probability which should be exceeded by the predictive value of the test. When the benefit--cost ratio is low, a test with a very high predictive value is required to exceed the threshold probability. On the other hand, when the benefit--cost ratio is high, even a test with a low predictive value would be of use to the physician in making the decision to treat the patient. Within this framework, a number of clinical situations could be evaluated and problems requiring the development of highly predictive laboratory tests (low benefit--cost ratios) could be identified. Too much emphasis in laboratory medicine has been placed on the "laboratory" and not enough on the "medicine". How important is the coefficient of variation when the benefit--cost ratio is high? Tests can not be developed or selected appropriately in a therapeutic vacuum.

Adolescent↗
PubMed1988

[Respiratory function evaluation in esophageal surgery. Predictive value of tests].

In the context of major surgery the predictive significance of respiratory function tests in relation to postoperative pleuro-pulmonary complications is assessed. A statistical analysis is performed on a series of 85 oesophagectomy after thoracotomy and laparotomy. The most significant respiratory function indices are found to be those relating to volume restriction and the Mottley index.

Adult↗
PubMed1982

Application of the predictive value model in the analysis of test effectiveness.

There are four levels at which laboratory tests and procedures can be evaluated relative to their effectiveness: 1. Analytical analysis of laboratory test: precision, accuracy, analytical sensitivity, and analytical specificity. 2. Diagnostic analysis of laboratory test: diagnostic sensitivity, diagnostic specificity, Youden index, likelihood ratio, and ROC curve. 3. Operational analysis of laboratory test: predictive value of positive result, predictive value of negative result, efficiency, discriminant function, and so forth. 4. Medical decision-making analysis of laboratory test: threshold probability, cost-benefit analysis, and solving the decision tree. Laboratory test selection can occur at any level, without knowledge of the test's evaluation and performance at the other levels. Alternatively, the development of new laboratory tests can proceed from level 1 to level 4, or vice versa. Unfortunately, the former is usually the case and most of the tests in use today have never been evaluated at the medical decision-making level. In evaluating clinical laboratory tests, it is essential that the laboratory have at its disposal simple ways to analyze sets of data. The predictive value model has proven to be effective in designing test strategies and evaluating the usefulness of laboratory tests. The widespread use of computers in laboratory medicine should permit this approach to data analysis to become routine in the next few years.

Acid Phosphatase↗
PubMed1996

Prognostic models for the probability of achieving an ongoing pregnancy after in-vitro fertilization and the importance of testing their predictive value.

The aim of this study was to create reliable models to predict the probability of achieving an ongoing pregnancy during in-vitro fertilization (IVF) treatment: model A, at the start of the first treatment, model B at the time of embryo transfer, and model C, during the second treatment at the end of the first IVF treatment. Prognostic models were created using data from the University Hospital Nijmegen (n = 757) and applied to the data from the Catharina Hospital Eindhoven (n = 432), The Netherlands, to test their predictive performance. The predictions of model B (made at time of embryo transfer) were fairly good (c = 0.672 in the test population). For instance, 93% of the patients who had a predicted probability of achieving an ongoing pregnancy of < 10% did not achieve an ongoing pregnancy. However, the predictions of the other two models (A and C) for Eindhoven were less reliable. The predictive value of model C was fairly high in Nijmegen (c = 0.673). Its poor performance in the test population may be explained partly by differences in effectiveness of the ovulation stimulation protocols and the decision about when to discontinue the cycle. Thus, before using prognostic models at an IVF centre, their reliability at that specific centre should be tested.

Evaluation Studies as Topic↗
PubMed1990

Is blood pressure an important variable in research on aging and neuropsychological test performance?

Regression analyses using Blood Pressure, Age, and the multiplicative effect of Blood Pressure and Age as predictors of performance (on selected tests from the Halstead-Reitan neuropsychological test battery) were done. Three hypotheses were tested with subjects ranging in age from 20 to 72 years of age: (1) blood pressure values predict neuropsychological test performance over a wide range of hypertensive and normotensive blood pressure values; (2) blood pressure predicts performance within the narrower range of normal and borderline values; (3) blood pressure X age interactions, when observed over this age and education range, are such that negative blood pressure effects on performance are larger for younger than older subjects. Regression analyses confirmed each of these hypotheses and indicated that strength of prediction was not reduced when participants free from hypertension-related complications and medication were tested. Blood pressure X age interactions were seen for Trailmaking-B Test and the Tactile Performance Test-Localization for the primary sample. However, only Blood Pressure main effects were observed for the Average Impairment Rating, the Categories Test, TPT-Memory and TPT-Localization when age, sex, and education were controlled. Implications of these findings for the role of blood pressure in aging research and for longitudinal studies with subjects free from the need for treatment with antihypertensive medications are discussed.

Adult↗
PubMedDate not supplied

[Predictive value of rapid tests of cognitive condition in traumatic head injury].

INTRODUCTION: Neuropsychological assessment after head injury (HI) is sometimes not possible because of the physical and/or cognitive condition of the patient, or the lack of neuropsychological specialists at the hospital. Therefore clinical scales and rapid tests are used to obtain information about the severity of the lesion and the general cognitive condition. OBJECTIVE: To determine whether the rapid clinical scales used to assess the severity of HI (Glasgow Coma Scale, GCS), presence or absence of post-traumatic amnesia (Galveston Orientation and Amnesia Test, GOAT) and general cognitive condition (Mini-Mental State Examination, MMSE, and Short Test of Mental Status, STMS) predict the cognitive condition one year after the head injury. PATIENTS AND METHODS: We made a prospective, longitudinal, observational study of 100 persons of both sexes with HI, assessed on admission by the Neurosurgical Department, and one year after the trauma in the Outpatient Clinic. Clinical scales were used to assess the severity of HI, cognitive screening tests, neuropsychological attention, linguistic, memory and practical constructive tests were also done. Statistical analysis was by simple regression. RESULTS: The GCS only explained a small percentage of the results obtained for immediate memory. The GOAT predicted the linguistic and verbal memory test performance. The MMSE and STMS explained a high proportion of the execution of neurophychological tasks (attention, linguistic, memory and practical construction) one year after the trauma. CONCLUSIONS: With the MMSE and STMS valid results may be obtained when it is not possible to carry out general neuropsychological assessment.

Adult↗
PubMed1983

Predictive value of serologic tests.

An analysis of serologic tests for treponemal disease performed in Australian aboriginal communities is used to illustrate factors influencing the predictive value positive of serologic tests. Simple extrapolation of predictive value estimates, from prevalence, sensitivity, and specificity data, is complicated by variation of specificity between strata of a population, and the weighting of true positive and false positive results produced by the criteria for selecting individuals for testing. The predictive value positive of a particular test is greatest when it is used for incident cases suspected of having a disease, but lower when the same test is used to screen a whole population unless longitudinal data are available to exclude individuals with past disease. Preferential testing of individuals without active disease may produce very low predictive values. Empirical estimation of the predictive value of tests provides objective guidelines for decision making and enables increased predictability by modification of testing criteria.

Adolescent↗
PubMed1990

Serological markers and celiac disease: a new diagnostic approach?

We analyze the diagnostic efficacy of two celiac disease serological markers: anti-gliadin (IgA and IgG class) and anti-endomysium IgA-class (EmA-IgA) antibodies applied to 336 serum samples from celiac patients on both gluten-challenge and gluten-free diets, and a control group. The anti-gliadin and anti-endomysium antibodies levels were significantly higher among the gluten-consuming celiac patients than in the other groups. The greatest efficacy in diagnosing celiac disease was achieved in the Ema-IgA class test. The IgA-class anti-gliadin antibodies proved to be more specific, with a higher positive test predictive value than the IgG-class anti-gliadin antibodies, whereas the latter proved to be more sensitive, with a higher negative test predictive value than those of the IgA-class anti-gliadin antibodies. Our results also demonstrate that the simultaneous assessment of anti-gliadin IgA- and IgG-class antibodies constitutes a valid test in selecting patients suspected of having celiac disease. In turn the EmA-IgA antibodies constitute a confirmative test for indication of an intestinal biopsy.

Adolescent↗
PubMed1991

Evaluating the sensitivity and predictive value of tests of recent infection: toxoplasmosis in pregnancy.

The diagnosis of maternal infection in early pregnancy depends on tests which are sensitive to recent infection, such as specific IgM. Two types of test are considered: those where the response persists for a period following infection and then declines, such as IgM, and those whose response increases with time since infection, such as IgG-avidity. However, individuals vary in their response to infection, and it may not always be possible to determine whether an infection occurred during pregnancy or before it. Mathematical methods are developed to evaluate the performance of these tests, and are applied to the diagnosis of toxoplasmosis in pregnancy. It is shown that, based on existing information, tests of recent infection are unlikely to be both sensitive and predictive. More data on these tests are required, before they can be reliably used to determine whether infection has occurred during pregnancy or before it.

Animals↗
PubMed1979

The impact of disease prevalence on the predictive value of laboratory tests in primary care.

The predictive value of any diagnostic process is related to the sensitivity and specificity of the test and the prevalence of the underlying pathology for which the diagnostic testing is accomplished. Prevalence is the most important, but least understood, factor affecting the usefulness of a test result. For each accomplished test which is not helpful in either supporting a diagnosis or assisting in a differential diagnosis, the health care cost is increased without a corresponding benefit in the value of the information obtained.

Clinical Laboratory Techniques↗
PubMed1988

Serological tests in leprosy. The sensitivity, specificity and predictive value of ELISA tests based on phenolic glycolipid antigens, and the implications for their use in epidemiological studies.

This paper examines the sensitivity and specificity of two ELISA assays for IgM antibodies to Mycobacterium leprae, one employing natural phenolic glycolipid and the other employing a synthetic disaccharide glycoconjugate as antigen. Estimates of sensitivity and specificity are derived, based on a panel of sera from leprosy cases in Malawi and various non-leprosy controls from the UK. Though both assays were able to identify a high proportion of multibacillary patients, neither was able to detect a high proportion of paucibacillary patients without considerable loss of specificity. The implications of the inverse relationship between sensitivity and specificity are discussed with reference to the predictive value of such tests in such areas as Malawi, where the large majority of cases are paucibacillary.

Enzyme-Linked Immunosorbent Assay↗
PubMed1977

Scales for measuring health belief model dimensions: a test of predictive value, internal consistency, and relationships among beliefs.

Critiques of research on the Health Belief Model have been directed at the need for: (1) applying the Model to behavior related to chronic illness; (2) multivariate testing of the major dimensions of the Model; (3) developing reliable scales; and (4) explicating the relationships among the beliefs. In an attempt to respond to these concerns, data are presented from a prospective study of mothers' adherence to a diet regimen prescribed for their obese children. The Model components were found, both singly and in combination, to be correlated with the study's measure of dietary compliance. Multiple regression analysis utilizing five belief indices accounted for a substantial portion of the variance in children's weight change. Questionnaire items employed in creating indices for each Model dimension are presented, together with discussion of the internal consistency of each index. Belief intercorrelations appear to demonstrate that distinct Model dimensions exist.

Adolescent↗
PubMed2004

NBME Obstetrics and Gynecology clerkship final examination scores: predictive value of standardized tests and demographic factors.

OBJECTIVE: To assess the predictive value of standardized tests and demographic factors on performance on the National Board of Medical Examiners (NBME) Obstetrics and Gynecology (OBGYN) examination. STUDY DESIGN: The study included 171 students who rotated through obstetrics and gynecology from 1992 to 2001. Correlations between NBME OBGYN scores and United States Medical Licensing Examination (USMLE) step 1, MCAT and GPA scores, and temporal and demographic factors were analyzed. RESULTS: The mean Medical College Admission Test (MCAT), NBME and USMLE step 1 scores were 24.03, 67.47 and 194.53, respectively. Significant correlations with NMBE OBGYN were USMLE step 1 scores (r = .517, p < 0.001), MCAT scores (r = .481, p < 0.001), faculty evaluation grade (r=.223, p <0.01), OBGYN residency interest (r= .179, p < 0.05) and female gender (r=.157, p< 0.05) with a significant negative correlation with clerkship duration (r = -.208, p < 0. 01). On logistic regression analysis, USMLE, MCAT, academic year and faculty evaluation grade were independently predictive of NBME OBGYN scores. All preclinical standardized tests showed positive correlation with progressive academic years and decreasing student age. and decreasing student age. CONCLUSION: USMLE step 1, MCAT scores and faculty evaluation grades were predictive of NMBE OBGYN scores. They may be helpful in assessing third-year medical students in need of special supervision and assistance.

Adult↗